Shower Faucet Installation

Wondering how to replace a shower valve when valve access is bad or nonexistent, when the old pipes are galvanized steel, and when you want to go from a two-handle to one handle valve with temperature-balancing and anti-scald features? We show you how to solve these common problems.

Overview: 3 common shower valve replacement problems

If your bath or shower faucet drips, you can fix it
with a few inexpensive replacement parts. (If
the spout and handles are worn, you can
change them out, too.) But if it’s a new style
you’re after or features like preset temperatures or anti-scald
protection, it’s time for replacement. Installing a
new shower faucet is a straightforward process of connecting
the new valve to the old pipes. Sometimes all you
need are the manufacturer’s instructions and some basic
plumbing know-how. But it isn’t that easy very often.
This article will focus on three complications that installation
manuals and plumbing books ignore.

Problem 1: No access panel

Photo 1: Mark the location

Punch a hole
into the wall
behind the
faucet to mark
the location of
the access panel.
Just slip a long
screwdriver
alongside the
tub spout nipple
and push.

Photo 1A: Location on backside wall

Poke a hole from the bathroom side. Don't try to measure and guess.

Photo 2: Cut an access hole

Cut a hole
3 in. smaller
than the access
panel so you can
see the exact
pipe locations.
Then mark and
cut the full-size
access hole.

Photo 3: Mount the access panel

Glue the
access
panel's frame
into place and
snap on the
cover after
you've installed
the new faucet.
You can paint
the panel to
match the wall.

To replace the faucet, you have to work
inside the wall. Some homes have a
removable panel in the next room
behind the faucet. If you don’t
have an access panel, you might
be able to replace the faucet by
cutting a hole in the shower
surround (Problem 3 below), but the
best solution is to install a
paintable plastic panel behind
the faucet. You’ll find them in various
sizes at plumbing suppliers, some
home centers or online (search for
“access panel”). Buy a panel that’s at
least 14 x 14 in. If you don’t want
to install a panel because it would be an
eyesore, an oversized cover plate inside
the shower surround is another option
(Problem 3 below). If you already
have an access panel but it’s too low to
provide easy access to the faucet, you can
install a second panel above the existing
one.

Don’t try to position the access hole
by taking measurements. Instead, remove
the tub spout or faucet handles and
punch a marker hole through the wall
(Photo 1). If the wall is plaster rather
than drywall, use a drill and a long bit
instead of a screwdriver. Before you cut a
hole sized for the access panel, cut a
smaller hole (Photo 2). That way, you
can see exactly where the pipes and
valves are located and position the full-size
hole for best access to them. Use the
access panel frame as a template to mark
the full-size hole. To avoid damaging the
frame of the panel, install it after you’ve
replaced the faucet (Photo 3).

Problem 2: Galvanized steel pipe

Photo 1: Disconnect the union fittings

Unscrew the ring nuts that fasten the union fitting
to the faucet body. Then unscrew the union fittings
from the supply lines.

Photo 2: Cut the shower riser

Cut the shower riser with a reciprocating saw or
jigsaw. Cut slowly and gently so you don't loosen
the connections above.

Photo 3: Add a galvanized pipe coupler

Connect the cutoff
shower pipe using a
coupler designed for galvanized
pipe. The coupler
won't work with copper
pipe, so screw a short galvanized
steel nipple into a
copper fitting.

Unlike copper or plastic, steel pipes are joined with threaded,
screw-together connections. So you can’t simply cut the hot
and cold supply pipes. That would remove the threaded ends
and you’d have no reliable way to connect new pipe.

To preserve those threaded ends, unscrew the union fittings
that connect the supply lines to the faucet (Photo 1). You can
leave the spout nipple connected to the faucet and remove it
along with the valve. If the faucet is connected to a showerhead,
cut the “shower riser” pipe (Photo 2). This pipe isn’t under constant
pressure, so you can reconnect it with a special coupler later.

Connect the new faucet as shown in Photo 3. To connect the
cutoff shower riser, use a special compression coupler designed
for galvanized steel pipe (called a “Dresser” coupling). For a better
seal and easier installation, apply Teflon pipe sealant to the
coupler’s threads and rubber seals. Run the shower and check
the coupler for leaks. If you find one, tighten the coupler’s nuts.

Figure A: New Shower Valve Connections to Galvanized Pipe

Make the connections shown when going from old galvanized pipe to copper pipe and adding the new valve. Also add new shutoffs.

Photo 3: Mount the cover plate

If you have a two-handle faucet, it’s easiest
to replace it with another two-handle
model. If you want the convenience of a
single handle, you’ll have to hide the two
holes left by the handles. An oversized
cover plate does just that. Plus, it covers an
access hole, possibly allowing you to skip
adding an access panel. Keep in mind that replacing a faucet
using this smaller hole can be difficult if
not impossible—a large access panel
makes the job much easier. You’ll find
oversized cover plates (about $23) at plumbing
supply stores or online (search for “renovation
cover plate”).

To install a single-handle faucet, you’ll
have to cut a hole into your shower surround.
If your surround is fiberglass or
acrylic, cut the hole using a jigsaw and a
fine-tooth blade (a coarse blade causes
more vibration, which can crack the surround).
Apply strips of masking tape to
the surround to avoid scratching or chipping
the surface. Run the saw at full speed,
but push it slowly and gently along the cut
mark. If you feel the blade hitting a pipe
inside the wall, stop immediately and continue
past the pipe using a hacksaw blade.

To cut tile, use a rotary tool
equipped with a tile-cutting bit (Photo
1). Set the cutting depth of the bit at 1/4
in. and make the first pass. Make more
passes, setting the bit 1/4 in. deeper each
time until you’ve cut completely through
the surround. If you don’t own a rotary
tool, you have a few other options: You
can try a jigsaw and ceramic tile blade
(about $5). These blades cut softer tile well. If
you find that your tile is too hard, drill a
series of 1/4-in. holes through the tile and
wall using a carbide ceramic tile bit (about $5).
Drill the holes close together so there’s little
or no space between them. Then cut
any material between the holes with the
ceramic tile jigsaw bit.